How to check if variable is array?... or something array
I want to use a foreach loop with a variable, but this variable can be many different types, NULL for example.
So before foreach I test it:
if(is_array($var)){
foreach($var as ...
But I realized that it can also be a class that implements Iterator interface. Maybe I am blind but how to check whether the class implements interface? Is there something like is_a function or inherits operator? I found class_implements , I can use it, but maybe there is something simpler?
And second, more important, I suppose this function exist, would be enough to check if the variable is_array or "implements Iterator interface" or should I test for something more?
If you are using foreach inside a function and you are expecting an array or a Traversable object you can type hint that function with:
function myFunction(array $a)
function myFunction(Traversable)
If you are not using foreach inside a function or you are expecting both you can simply use this construct to check if you can iterate over the variable:
if (is_array($a) or ($a instanceof Traversable))
foreach can handle arrays and objects. You can check this with:
$can_foreach = is_array($var) || is_object($var);
if ($can_foreach) {
foreach ($var as ...
}
You don't need to specifically check for Traversable as others have hinted it in their answers, because all objects - like all arrays - are traversable in PHP.
More technically:
foreach works with all kinds of traversables, ie with arrays, with plain objects (where the accessible properties are traversed) and Traversable objects (or rather objects that define the internal get_iterator handler).
(source)
Simply said in common PHP programming, whenever a variable is
and is not
you can use foreach on it.
You can check instance of Traversable with a simple function. This would work for all this of Iterator because Iterator extends Traversable
function canLoop($mixed) {
return is_array($mixed) || $mixed instanceof Traversable ? true : false;
}
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